Science and Language
by alecsangryface
Summary: They don't share many interests, but they make it work
**A/N: Written for 600 followers on my tumblr alecsangryface, I'll never stop the self-promo. Ridiculously fluffy Lightwood sibling bonding times. If you want to review, it would be most welcome :D**

The library in the Institute was exactly like any other room in the building, full of dust and devoid of decadence. However, unlike any other room, it was a frequent stomping ground of the two eldest Lightwood children. Alexander and Isabelle Lightwood spent more time in the library than they did anywhere else, the quiet calm of the space mostly soothed the stresses of their everyday life and provided a working place for their personal projects.

Alec was sat in a deep crimson high backed velvet arm chair that seemed to swallow him almost whole. He had one of his legs tucked up to his chest and the side of his head resting on that knee, as his eyes scanned the pages of the book that he had balanced on his other leg. A pen was held loosely in his right hand and only moved when he passed it under and over his finger when an errant thought puzzled him long enough for his stillness to fade.

He barely spared Isabelle a glance when she entered the room, or as she moved an armchair, her armchair, closer to him, or as she went to and fro with large stacks of books that hardly wobbled as she carried them. He did spare her a glance when he heard the rustling of paper unfolding.

In front of her chair, she had laid out a large piece of dark grey paper on the floor and held the corners down with four books. _In the Name of Eugenics: Genetics and the Uses of Human Heredity_ the book closest to Alec read.

"What're you doing?" Alec asked softly. He didn't want to interrupt the steady progress Isabelle was making in ordering the books she had gathered into categories that were arbitrary to Alec,but undoubtedly clear to her.

"Making a Lightwood family tree" She replied easily, another book softly dropping to the top of one of the piles, "I want to see how often we cross with other families"

He huffed a surprised laugh, "Why the book about eugenics then?"

"I might get bored" She shrugged, her eyes flickered to meet his and they both started laughing. They both knew she wasn't going to get bored and it was _very_ likely that Alec would have to drag her away from her project in the early hours of the morning demanding that she get at least an hour of sleep.

They settled into relative silence after that, the only noise being the occasional turn of the page, or the soft scratch of pens on paper. After a couple of hours, Alec got up to stretch his legs out and get them some leftover Chinese food from the night before. He left a box of noodles close enough to Izzy so she could reach it, but made sure to keep it well away from her work. She tended to get militant about grease stains, and he was _not_ going risk his life more than he needed to. He need not have worried because Izzy immediately snatched the box up.

Now that he was stood up, Alec took the opportunity to see what books could possibly make Izzy's project so convoluted. He wasn't surprised to see the Institutes many copies of births, marriages and deaths Clave records or the old and battered copy of _A Shadowhunter's Guide to: The Great Families_. What did surprise him were the volumes upon volumes of European mundane censuses.

"What're you working on?" Izzy asked around a mouth full of noodles as he settled back into his chair. Alec raised an eyebrow at her until she swallowed and mouthed sorry.

"Just some translating stuff" He picked his book back up to bare the cover _Romeo and Juliet_ to her. She nodded knowingly.

"So you're nearly done with it then?" Izzy asked, easily making conversation as she continued with her task. From where he was sitting, Alec could see her perfect cursive appear on small terracotta note cards, she had already made a significant dent in the stack of blank ones. He wondered how far back she had gone already.

"Yes, thank the angel! I don't know why I started with it. I hate it!" Izzy snorted. Alec had read every Shakespeare play at least twice over and he decided that translating them to Modern English would keep his language skills sharp. He stretched his fingers one last time before opening the book and picking up his pen once more.

They made easy conversation as they worked, talking about Max and their parents, hunts they had been on, and hunt they were going on. Alec was especially grateful for Izzy in those moments. He knew she was desperate for him to talk about what was getting him so stuck in his own head, but he wasn't ready to and she respected that.

"There was never a story more full of pain than the story of Romeo and Juliet" Alec quoted his own words sarcastically. Izzy looked up from the manuscript in her lap, brow still furrowed from where she had been concentrating "I don't know, I think my story of having to translate that had more pain, but I'm not the greatest word smith to have ever live am I?"

Izzy rolled her eyes at her and didn't bother to dignify him with a response, after all she did want to work on her project without having to listen to him complaining about stupid he thought Romeo was.

They had talked about his hate of _Romeo and Juliet_ many times before. Or rather Alec had talked, and talked, and talked and Izzy had listened because she had never heard her brother speak at length before. Ever since they were children Alec had been of few words, preferring to get straight to the point, bluntness to a point where it was sometimes insensitive. Apparently though he was a man of many words when he had particularly strong feelings about something.

Izzy grunted when she looked back down at her book. It was frustrating that it took her so long to read and only because it was written in Danish. She knew some languages, like French and Spanish, and she could read Latin if she worked at it long enough, but she much preferred science. It was a universal language.

"Where are the Danish to English dictionaries?" She asked Alec before he could get up to find his next play. If she remembered the order he was going in correctly, he would be working on _Hamlet_ next which meant he was going to be in a much better mood.

"In the dictionary section. Why? What're you looking at?" He slid off his chair and crawled over to the tiny scrap of space next to her on the floor. He barely fit until he shoved the armchair Izzy had moved over away. She dropped the book into his lap and pointed her finger harshly against the page.

' _Husstandsmedlemmer'_ the word she pointed at read.

"Household members?" Alec asked, confused, "What's up with that?"

"I can't speak Danish" Izzy said tiredly but she produced a post-it-note from somewhere and wrote 'household members' on it, then stuck it over the Danish word.

"I'll translate for you" Alec offered, his eyes already scanning the page to translate the words. It was as easy as reading English or one of the many other languages he knew, "Why do you need this anyway?"

"Are you sure?" Izzy replied hopefully. Alec nodded and she quickly hugged him, her hair getting in his mouth as she did so. He recoiled from her, spluttering excessively until the hair was gone and raised his eyebrows to prompt her into answering his question.

"The Clave records only go so far back" She explained, lifting up the book about the great families and flipping it to one of the back pages. They had seven hundred and eighty two years to cover if they wanted to trace their line all the way back to Johnathan Shadowhunter, the book only went six hundred years when the Institutes were first built. Despite that the Lightwood name was still appearing as Lightwood and not some earlier branch, "And I found something in one of these books that pointed in the direction of Johnathan being Danish. I narrowed it down to one area Denmark of course but there's still a lot to go through"

Alec didn't respond. Instead he just reached around Isabelle for her post-it-notes and began translating. The censuses were simple, he only had to translate some simple words, but the manuscripts detailing different 'police' reports were more time consuming.

They were so swept up in their work that they didn't realise how late it was getting until they could barely see words on the pages they were reading. Isabelle started gathering up her note cards that were still loose as she hadn't managed to stick them down in their correct places on the tree. Alec took that as a signal to gather up the books into a more organised mess at least. There was no point taking them all back to their shelves since they would no doubt need them when they revisited the project.

For the next two weeks whenever they two of them had any free time, they were in the library either translating or piecing together the final parts of the Lightwood family tree. Jace had asked what they were doing, but confessed that there was no way he was taking part when they asked if he wanted to join them. He claimed that it sounded like the most boring task ever, secretly he declined because Alec and Izzy needed an excuse to spend more one-on-one time with each other.

"I have it!" Alec crowed, startling Izzy where she was drawing in parabatai lines. The line between Jace and Alec had a wiggle in it now. It made her smile as if their bond was different to the other parabatai bonds in the family tree.

"Johnathan Shadowhunter's eldest daughter Abigail, married the eldest Lightwood son of the Lightwood family who had all been turned by David" Alec summarised, pointing at his careful notes of translation on the notebook he'd commandeered.

Izzy squealed and jumped to her feet, pulling Alec up with her so the book in his lap tumbled to the floor. She hugged him tight and laughed into his ear.

"I can't believe the Lightwoods go that far back! And to have Shadowhunter blood in our line!" Izzy breathed. She had released Alec and was staring off into space, "I never believed Dad when he said our family was one of the oldest"

Alec smiled and retrieved the book from the floor. Finding the page he had lost proved a lot more difficult than first expected, but it was a necessary evil if they wanted to find out the name of that particular Lightwood that Alec had gotten too excited to write his name down.

 _James Lightwood_

The final piece of the puzzle. As Izzy stuck the final note cards down and they stepped back to survey their work, it was a bittersweet moment. They had finished their task, but it was over. Two weeks, more for Izzy, dedicated to this pursuit for it to just end.

"So let's do the Trueblood line next?" Alec said, dropping an arm over Isabelle's shoulders and pulling her tight into his side, when he saw her sad smile. She looked up at him with the biggest smile on her face that Alec would have agreed to map out every single Shadowhunter family tree with her if she asked.

"I think we should call time on this" Izzy whispered, letting her head fall onto Alec's shoulder, "Besides you still have all your plays to translate. I could help with that if you want?"

She turned hopeful eyes to Alec again, and the denial on his tongue died, "If you can learn enough Old English and how to translate it, sure. But let's not let it take us over like this did?" He waved a hand over the reams over paper still on the floor.

"Deal"

"Where are we going to put this?" Alec asked eventually.

After a long conversation, and an even longer time rolling up the pages for better manoeuvrability, they decided that it would be easiest to display in an old ballroom that hadn't been used in at least a century. It spanned the entire west and north wall, and it made a significant dent into the eastern wall.

Isabelle ran a hand over her name and the lines that connected her with her immediate family. She looked wistful, "I wonder what our partners names will look like up here" she whispered.

Alec rolled his eyes. He caught the unspecified gender and silently sent a thank you to Raziel for blessing him with a sister like her, as he caught a glimpse of the many Lightwood family crests Max had doodled on the outskirts of the paper.

"This bit is my favourite though" Alec tapped a finger on the line that joined him and Izzy. She smiled up at him and wound an arm through his, a sort of hug. She was just as grateful for him as he was her, not many brothers would have given up their own pursuits as easily as he had done to help her.

It was a wonderful feeling having finished what she had been working on for so long, but it was even better knowing that she was closer to her brother for it.


End file.
